1. Field of the Invention
The invention relates to a coaxial filter cigarette comprising a rod portion, an inner core of a tobacco and/or non-tobacco material smouldering substantially without residue, a sheath for the inner core, an outer jacket of a tobacco and/or non-tobacco material surrounding the inner core and its sheath, and a sheath for the outer jacket, as well as a filter portion.
2. Description of the Prior Art
A number of publications exist on so-called "coaxial smokable articles", i.e. in particular coaxial cigars or cigarettes having an inner core which is surrounded by a jacket of tobacco material. The basic principle of such a coaxial cigarette is for example known from FR-PS 998,556, the inner core consisting of a tobacco of lower quality which is surrounded by an annular jacket of tobacco of higher quality. This makes it possible to achieve savings with regard to the costs of the tobacco materials employed.
Further embodiments of such coaxial cigarettes are described in FR-PS 1,322,254, U.S. Pat. No. 3,614,956, U.S. Pat. No. 4,219,031, GB-OS 2,070,409, GB-PS 1,086,443 and DE-OS 3,602,846.
Furthermore, from U.S. Pat. No. 3,356,094 a coaxial cigarette is known having an inner hollow tube and an aerosol-generating zone with a narrow outlet; the production of this coaxial cigarette is however very complicated and thus expensive; moreover, the various components are separate from each other and this gives an unusual smoke pattern.
A coaxial filter cigarette of the type indicated is known from DE-PS 3,743,597 and comprises a rod portion and a filter portion; the rod portion includes an inner core of a material smouldering substantially free of residue, in particular tobacco material, a sheath for the inner core, an outer jacket of a tobacco and/or non-tobacco material coaxially surrounding the inner core and its sheath and a sheath for the outer jacket.
The filter portion comprises a filter core, an air-impermeable sheath for the filter core, a filter jacket and a sheath for the filter jacket.
The basic principle of this coaxial filter cigarette resides in that in the radial direction a distinction is made between two regions, i.e. the zone of the main heat source on the one hand and on the other hand the zone in which the major portion of the aerosol reaching the mouth of the smoker is generated. The heat-generating zone is in the outer jacket and the aerosol-generating zone is in the inner core of the rod portion.
A problem with such a design of a coaxial filter cigarette is the desired reduction of the secondary smoke which can only be achieved with great expenditure. Also, such a coaxial filter cigarette has an ignition potential similar to a conventional cigarette.
A further coaxial filter cigarette of this type is known from DE-PS 3,901,226. The latter also comprises a rod and a filter portion, the rod portion including an inner core of a material smouldering substantially free of residue, a substantially air-impermeable sheath, an outer jacket coaxially surrounding the inner core and its sheath and a sheath for the outer jacket. The filter portion is formed as coaxial filter having a filter core surrounded by an air-impermeable sheath and a filter jacket.
The zone required only as heat source and the zone in which the major part of the aerosol reaching the mouth of the smoker is produced are spatially separate. This has the essential effect that the smoke reaching the mouth of the smoker has a high proportion of components relevant to the flavour and a very low proportion of undesirable combustion products. Since the zone generating the heat is arranged in the inner core of the rod portion, the combustion products are shielded by the outer jacket of the rod portion and thereby given off largely via the main smoke and this can be utilized as one of several pre-requisites for the reduction of the secondary smoke.
Since however the mixture in the rod portion as a rule furnishes such large amounts of smoke that the coaxial filter element alone no longer suffices for the filtering, diffusion and ventilation elements are additionally arranged between the filter element and rod portion, possibly with further intermediate elements and outer passages.
A feature common to both the known coaxial cigarettes of this type is that an appreciable secondary smoke reduction can be achieved only by using special papers, in particular by cigarette papers of very low air permeability and with specific additives. However, due to the combustion of these special papers the main smoke then necessarily has an undesirably high content of carbon monoxide which can only be inadequately reduced by the known arrangements. This fact limits the possibility of reducing the secondary smoke.